[DlcSettingsUi] Aria-hides tooltip icon and removes it from tab order.

* Aria-hides the entire wrapper of text and tooltip, rather than the
  text divs individually.
* Removes the tooltip icon from the tab order, in line with other
  tooltips of the same style in OS Settings. The tooltip is not
  actionable, so it should not be tab-able to.

Bug: 1070712
Change-Id: I637909d4703a49cb35bbf7f32fb00afb1ffe2e7a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2219598
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773405}

chrome/browser/resources/settings/chromeos/device_page/dlc_subpage.html

@@ -45,17 +45,20 @@
     <iron-list id="list" items="[[dlcList_]]" preserve-focus risk-selection>
       <template>
         <div class="list-item settings-box two-line">
-          <div class="start primary">
-            <span id="name[[index]]" aria-hidden="true">[[item.name]]</span>
+          <div class="start primary" aria-hidden="true">
+            <span id="name[[index]]">[[item.name]]</span>
             <template is="dom-if"
                 if="[[includeTooltip_(item.description)]]">
+              <!-- Tooltip isn't actionable, so removed from the tab order -->
               <cr-tooltip-icon
+                  id="description[[index]]"
+                  tabindex="-1"
                   icon-class="cr:info-outline"
                   tooltip-text="[[item.description]]"
                   tooltip-position="bottom">
               </cr-tooltip-icon>
             </template>
-            <div id="size[[index]]" class="secondary" aria-hidden="true">
+            <div id="size[[index]]" class="secondary">
               [[item.diskUsageLabel]]
             </div>
           </div>
@@ -64,7 +67,8 @@
               id="remove-button-[[index]]"
               on-click="onRemoveDlcClick_"
               tabindex$="[[tabIndex]]"
-              aria-describedby$="name[[index]] size[[index]]">
+              aria-describedby$="name[[index]] size[[index]]
+                  description[[index]]">
             $i18n{removeDlc}
           </cr-button>
         </div>